This invention relates to a cleaning method for use in a semiconductor exposure apparatus wherein a thin plate-like substrate such as a semiconductor wafer is held on a movable table (stage) and is processed by predetermined treatment. In another aspect, the invention is concerned with a method of cleaning a holding surface of a wafer chuck in such an exposure apparatus, or with a whetstone for the cleaning. In a further aspect, the invention is directed to a device manufacturing method using such an exposure apparatus.
In semiconductor exposure apparatuses, a thin plate-like substrate such as a semiconductor wafer having a photoresist coating is held by attraction on a movable table, and a reticle pattern is transferred to the substrate. If the substrate holding surface of the movable table is contaminated or if foreign particles are deposited thereon, the substrate held thereon is contaminated or local deformation of the substrate is caused at the portion where particles are deposited between the substrate and the substrate holding surface, which results in a decrease of yield or process quality, as is known in the art. It is, therefore, necessary that the substrate holding surface be cleaned periodically, to avoid these problems.
Conventionally, the cleaning of a substrate holding surface is made manually by polishing the substrate holding surface with the use of a whetstone or cleaning it with a cloth and solvent.
However, manually cleaning the holding surface quite uniform requires skills and, therefore, the quality is not even, depending on the skill of the operator or on the work on that day. Further, much time is necessary for the work, and it leads to a decrease of operation efficiency of the apparatus. From the viewpoint of the structure of the apparatus, it is necessary to provide a maintenance area for the cleaning, and it causes enlargement of the floor area for the apparatus or of the area occupied. Furthermore, in a small environment as represented by recent SMIF, doing the work itself while keeping a door of the apparatus open causes a factor for decreasing the cleanness inside the apparatus.
It is an object of the present invention to make it practicable to clean a substrate holding surface uniformly and in a short time without relying on the skill of an operator.
It is another object of the present invention to make it practicable to clean a substrate holding surface without lowering the cleanness inside the apparatus.
It is a further object of the present invention to reduce a maintenance area required for the cleaning.
In accordance with an aspect of the present invention, there is provided an exposure apparatus, comprising: a chuck having a holding surface for holding a substrate; a stage for holding said chuck; a moving mechanism for moving said stage; an urging mechanism for holding a whetstone and for urging it against the holding surface; and a conveying mechanism for conveying the whetstone to said urging mechanism; wherein said stage is moved while the whetstone is urged against to the holding surface, for cleaning the holding surface.
The apparatus may preferably further comprise a conveying hand mechanism for conveying the substrate to the holding surface, wherein said conveying mechanism may use said conveying hand for conveyance of the whetstone.
The apparatus may further comprise a transfer member retractably protruded from the holding surface, wherein said conveying mechanism may transfer the whetstone between it and said urging mechanism by use of said transfer member as the same is protruded from the holding surface.
The urging mechanism may include a pressing mechanism for pressing the whetstone against the holding surface by a predetermined pressure.
The whetstone may be provided with a magnetic material, wherein said urging mechanism may be operable to perform mounting and demounting of the whetstone by use of an electromagnet.
The whetstone may be formed with a recess, and said urging mechanism may have a protrusion engageable with the recess.
The movement of said stage relative to the whetstone may comprise one of rectilinear motion, circular motion and a combination of rectilinear motion and circular motion.
The apparatus may further comprise a chamber having an opening through which the whetstone can be introduced into said exposure apparatus.
Said conveying mechanism may be operable to pick up the whetstone, as accommodated in a container cassette having been introduced into said exposure apparatus, out of the cassette and to convey it toward said urging mechanism.
In accordance with another aspect of the present invention, there is provided a cleaning method, comprising the steps of: conveying a cleaning whetstone to a holding surface of a wafer chuck by use of a wafer conveying mechanism for conveying a wafer; and cleaning the holding surface with the whetstone.
In accordance with a further aspect of the present invention, there is provided a cleaning method, comprising the steps of: conveying a cleaning whetstone to a holding surface of the wafer chuck; urging the cleaning whetstone against the holding surface; and moving a wafer stage relatively to the whetstone, whereby the holding surface is cleaned.
In accordance with a yet further aspect of the present invention, there is provided a cleaning whetstone for cleaning a holding surface of a wafer chuck in an exposure apparatus, comprising: a cleaning surface; and a holding portion engageable with a member for holding the whetstone, said holding portion having at least one of a step and a hole.
Said holding member may be provided by at least one of (i) an urging mechanism for urging the whetstone against the holding surface of the wafer chuck, (ii) a transfer member protruded from the holding surface of the wafer chuck, (iii) a positioning member for a whetstone cassette for accommodating the whetstone therein, and (iv) a hand mechanism for holding the whetstone by attraction and for conveying the same.
In accordance with a still further aspect of the present invention, there is provided a device manufacturing method, comprising the steps of: preparing an exposure apparatus as recited above; cleaning a holding surface for holding a substrate; and exposing the substrate with radiation.
The method may further comprise coating the substrate with a resist before the exposure, and developing the substrate after the exposure.